Molecular studies of pressure/temperature-induced structural changes in bovine β-lactoglobulin

beta-Lactoglobulin in 50 mm Tris/HCl buffer at pH 7 was subjected to combined pressure and temperature treatments using a central composite experimental design. Pressures up to 294 MPa, temperatures up to 62 degreesC and processing times up to 30 min were studied. The molecular structure at the secondary and tertiary levels was analysed post-processing using far- and near-UV circular dichroism. It was found that, although the pressures applied were moderate, the far-UV circular dichroism spectra showed important changes corresponding to an increase in alpha-helix content. The tertiary structure was almost completely lost for the highest processing intensities. This suggests a transition to the molten globule state. The percentage change in molar ellipticity at 293 nm (tertiary structure) was found to be linearly connected to the three independent variables, hence possibly allowing process optimisation for that response. Pressure was found to be the most important parameter to bring about the molecular changes at the two molecular levels investigated. (C) 2004 Society of Chemical Industry.